The present invention relates to a method and an apparatus for reducing the acid gas and pollutants content in the combustion products, the acid dewpoint temperature and the level of corrosion of the waste-fired incinerators using either mass burning or refuse-derived fuel burning and their auxiliary equipment.
A general problem exists for municipal or industrial waste burning incinerators in how to efficiently and cost effectively control pollutants, acid gases, and damage to incinerators and their auxiliary equipment as a result of burning waste materials. More particularly, it has been found that the combustion of wastes results in the formation of hydrochloric acid, sulfur dioxide, sulfur trioxide and a number of other combustion by-products, which could cause amongst a host of other problems atmospheric pollution and subject the incinerator and their auxiliary equipment to the possible shortening of their service life.
A number of attempts have been made to date with other types of incinerators, i.e., fluidized bed combustors, by adding various sorbent materials to the waste or at different stages of the incineration process in order to reduce noxious gases and the level of corrosion.
For example, the Hokari et al. patent (U.S. Pat. No. 4,474,122) discloses adding earth metal carbonates into the fluidized bed portion of a fluidized incinerator. The additives are provided either by means of a screw feeder or together with air such that the powdery carbonates undergo a reaction with the acidic gases contained in the fluidized bed.
A different method for protecting incinerator surfaces is exemplified by the Kramer patent (U.S. Pat. No. 4,253,403). In particular, Kramer discloses mixing the incineration waste materials with additives such as limestone prior to combusting the materials in the incinerator. During operation of the incinerator, the waste materials and additive mixtures are then injected into the combustion zone such that the combined products provide a raised fusion temperature in order to promote increased reaction between the waste material and the additive.
Other arrangements include the Fuller et al. patent (U.S. Pat. No. 3,556,024) and the Rausing patent (U.S. Pat. No. 3,633,780). Each of these disclose methods for reducing corrosion or emissions through adding an alkali metal to the waste material prior to burning. These latter methods, however, can create several inefficiencies or can require an investment in equipment for pre-mixing the additive with waste materials.
Second, in order to fulfill state and federal environmental standards, a relatively high percentage of the noxious gases produced during the refuse incineration process would have to be removed. Prior art teachings, however, have not devised a method whereby the reduction of pollutants is optimized from a cost standpoint in order to comply with state and federal environmental standards with respect to emissions and ambient air levels and the like. A need thereby exists for an efficient, low-cost noxious gas control system that fulfills current environmental standards.